Comparison of the Carba NP, Modified Carba NP, and Updated Rosco Neo-Rapid Carb Kit Tests for Carbapenemase Detection

Burden and Management of Multi-Drug Resistant Organism Infections in Solid Organ Transplant Recipients Across the World: A Narrative Review

Solid organ transplant (SOT) recipients are particularly susceptible to infections caused by multidrug-resistant organisms (MDRO) and are often the first to be affected by an emerging resistant pathogen. Unfortunately, their prevalence and impact on morbidity and mortality according to the type of graft is not systematically reported from high-as well as from low and middle-income countries (HIC and LMIC). Thus, epidemiology on MDRO in SOT recipients could be subjected to reporting bias. In addition, screening practices and diagnostic resources may vary between countries, as well as the availability of new drugs. In this review, we aimed to depict the burden of main Gram-negative MDRO in SOT patients across HIC and LMIC and to provide an overview of current diagnostic and therapeutic resources.

Carba PBP: a novel penicillin-binding protein-based lateral flow assay for rapid phenotypic detection of carbapenemase-producing Enterobacterales

Rapid phenotypic detection assays, including Carba NP and its variants, are widely applied for clinical diagnosis of carbapenemase-producing Enterobacterales (CPE). However, these tests are based on the acidification of the pH indicator during carbapenem hydrolysis, which limits test sensitivity and speed, especially for the detection of CPE producing low-activity carbapenem (e.g., OXA-48 variants). Herein, we developed a novel rapid and sensitive CPE detection method (Carba PBP) that could measure substrate (meropenem) consumption based on penicillin-binding protein (PBP). Meropenem-specific PBP was used to develop a competitive lateral flow assay (LFA) for meropenem identification. For the detection of carbapenemase activity, meropenem concentration was optimized using a checkerboard assay. The performance of Carba PBP was evaluated and compared with that of Carba NP using a panel of 94 clinical strains characterized by whole-genome sequencing and carbapenem susceptibility test. The limit of detection of PBP-based LFA for meropenem identification was 7 ng mL-1. Using 10 ng mL-1 meropenem as the substrate, Carba PBP and Carba NP could detect 10 ng mL-1 carbapenemase within 25 min and 1,280 ng mL-1 CPE in 2 h, respectively. The sensitivity and specificity were 100% (75/75) and 100% (19/19) for Carba PBP and 85.3% (64/75) and 100% (19/19) for Carba NP, respectively. When compared with Carba NP, Carba PBP showed superior performance in detecting all the tested CPE strains (including OXA-48-like variants) within 25 min and presented two orders of magnitude higher analytical sensitivity, demonstrating potential for clinical diagnosis of CPE. IMPORTANCE This study successfully achieved the goal of carbapenemase activity detection with both high sensitivity and convenience, offering a convenient lateral flow assay for clinical diagnosis of carbapenemase-producing Enterobacterales.

Evaluation of Phenotypic Tests for Carbapenemase Detection in Enterobacteriaceae in Tunisia

Introduction: Resistance to carbapenems in Enterobacteriaceae is a challenge for public health. Carbapenemase production is the leading mechanism. This work aims to evaluate four phenotypic methods for carbapenemase detection in comparison with a molecular method. Materials and Methods: Thirty-seven nonrepeating Enterobacteriaceae strains with decreased susceptibility to ertapenem were included. Imipenem MIC, Modified Hodge Test (MHT), Neo-Rapid Carb Kit® and KPC, MBL, and OXA-48 Confirm Kit® were performed. Isolates were tested for blaOXA-48, blaNDM, and blaVIM genes by end-point polymerase chain reaction. The results of the molecular study were used as a reference test to determine the performances of the phenotypic tests. Results: Imipenem resistance does not seem to be a good marker for carbapenemase production with a sensitivity of 54% (95% CI: 38-71). MHT showed 82% sensitivity (95% CI: 65-91). Overall, the enzymatic test showed the best performances for carbapenemase detection with 100% sensitivity (95% CI: 89-100) and the best turnaround time. The characterization of carbapenemases classes by the combined discs test demonstrated 88% overall sensitivity (95% CI: 72-95). Conclusion: The results of this study support the combination of the enzymatic and the combined disc tests for carbapenemase detection in Enterobacteria.

Comparative Evaluation of Three Phenotypic Tests-Carba NP, Modified Carba NP and Rapidec Carba NP Test for Rapid Detection of Carbapenem Resistance in Blood Culture Isolates of Escherichia coli in an ICU Setting

Background

To determine the antibiotic resistance pattern, the prevalence of extended-spectrum beta-lactamases (ESBLs) and carbapenem resistance in blood culture isolates of E. coli. Further, we evaluated and compared Carba NP, Modified Carba NP and a kit-based Rapidec Carba NP test to detect carbapenem resistance rapidly.

Methods

Twenty-six carbapenem-resistant strains and four susceptible strains were selected. The three methods mentioned above were evaluated as per Clinical Laboratory Standards Institute (CLSI). These tests are based on biochemical detection of the hydrolysis of the beta-lactam ring of a carbapenem-imipenem, followed by the colour change of a pH indicator.

Results

Carba NP test was positive in 24 out of 26 isolates; the Modified Carba NP and Rapidec Carba NP tests were positive for all the isolates (26/26). All the carbapenemase non-producers (100%, 04/04) were negative.

Conclusion

Modified Carba NP is a more effortless and inexpensive alternative to the Carba NP test, allowing the detection of carbapenemase activity directly from bacterial cultures of Enterobacteriaceae. The test could be used in low-income countries with large reservoirs for carbapenemase producers and can be implemented in any laboratory worldwide.

Combating the menace of antimicrobial resistance in Africa: a review on stewardship, surveillance and diagnostic strategies

The emergence of antibiotic-resistant pathogens has threatened not only our ability to deal with common infectious diseases but also the management of life-threatening complications. Antimicrobial resistance (AMR) remains a significant threat in both industrialized and developing countries alike. In Africa, though, poor clinical care, indiscriminate antibiotic use, lack of robust AMR surveillance programs, lack of proper regulations and the burden of communicable diseases are factors aggravating the problem of AMR. In order to effectively address the challenge of AMR, antimicrobial stewardship programs, solid AMR surveillance systems to monitor the trend of resistance, as well as robust, affordable and rapid diagnostic tools which generate data that informs decision-making, have been demonstrated to be effective. However, we have identified a significant knowledge gap in the area of the application of fast and affordable diagnostic tools, surveillance, and stewardship programs in Africa. Therefore, we set out to provide up-to-date information in these areas. We discussed available hospital-based stewardship initiatives in addition to the role of governmental and non-governmental organizations. Finally, we have reviewed the application of various phenotypic and molecular AMR detection tools in both research and routine laboratory settings in Africa, deployment challenges and the efficiency of these methods.

Optimization of the rapid carbapenem inactivation method for use with AmpC hyperproducers

OBJECTIVES

Detection of carbapenemase-producing Enterobacterales (CPEs) is sometimes difficult with AmpC-hyperproducing Enterobacterales (AHEs), as they may falsely be classified as CPEs. Here, we present a rapid Carbapenem Inactivation Method (rCIM) optimized for AmpC producers (rCIM-A) that allows rapid and easy discrimination between AHEs and CPEs.

METHODS

Enterobacterales (n = 249), including natural AmpC producers, AHEs, CPEs and non-carbapenemase-producing carbapenem-resistant control strains were evaluated, using Carba NP, rCIM and rCIM-A. The rCIM-A differs from the rCIM by the addition of cloxacillin (400 μg/mL) to the initial antibiotic incubation step.

RESULTS

The rCIM-A yielded a sensitivity and specificity of 84.26% (95% CI: 76.00%-90.55%) and 99.29% (95% CI: 96.11%-99.98%), respectively, while those of the rCIM were 86.11% (95% CI: 78.13%-92.01%) and 80.85% (95% CI: 73.38%-86.99%), respectively; those of Carba NP were lower at 84.04% (95% CI: 75.05%-90.78%) and 91.37% (95% CI: 85.41%-95.46%), respectively, due to indeterminate results. The rCIM-A was capable of discriminating between AHEs and true CPEs, but still failed to identify OXA-23-producing Proteus mirabilis isolates and remained only partially reliable for identifying IMI-like producers and a few MBL (2 NDM-1, 1 LMB-1, 1 TMB-1 and 1 IMP-13) producers. One chromosomally encoded AmpC variant, MIR-10, gave repeatedly positive results using all three tests and was thus considered a false positive.

CONCLUSIONS

Specificity for AHEs greatly improved with the rCIM-A without altering the test performance for the other resistance mechanisms. It may replace the rCIM as a cheap, easy, rapid and accurate CPE detection test.

A profile of the GenePOC Carba C assay for the detection and differentiation of gene sequences associated with carbapenem-non-susceptibility

The novel GenePOC/Revogene Carba C assay (GenePOC, Québec, Canada; now Meridian Bioscience, Cincinnati, OH, USA) is a CE-IVD marked, FDA-approved qualitative in vitro diagnostic test for the detection of genes associated with carbapenem-non-susceptibility. Colonies of Enterobacterales can be directly tested without prior DNA isolation. The test consists of a fluorescent-based real-time PCR assay that runs on the centripetal microfluidic revogene platform, providing results within 70 minutes. The assay was evaluated in two studies comprising a total of 294 molecularly characterized clinical Enterobacterales isolates. The overall sensitivity for the detection of carbapenemase gene sequences with the GenePOC assay was 100% (95% CI, 98.4% to 100). Besides the common KPC, VIM, NDM and OXA-48-like carbapenemase genes, also the very variable IMP variants were all detected. The specificity of the assay was 100% (95% CI, 98.8% to 100%). In this article the performance of the GenePOC/Revogene Carba C assay is evaluated and other currently available methods for the detection of carbapenemases are reviewed.

In vitro cost-effective methods to detect carbapenemases in Enterobacteriaceae

The rise in carbapenemases-producing organisms has challenged the scientific community. Infections caused by these bacteria have limited treatment options. There are various types such as Klebsiella pneumoniae carbapenemase (Ambler class A), metallo-beta-lactamases of VIM-type, IMP-type, NDM-type (Ambler class B), and OXA-48-types (Ambler class D). An efficient strategy for detection of carbapenemase producers is important to determine the appropriate therapeutic modalities. In this study, four methods - Carba NP test, modified Carba NP (MCNP) test, carbapenem inactivation method (CIM) test, and Rapidec Carba NP kit test were evaluated. We evaluated an in-house MCNP test to detect carbapenemase production using a single protocol which gave reliable results. Furthermore, CIM using routine antibiotic discs gives good results. Both these tests were found to be cost-effective.

Carba NP test for the detection of carbapenemase-producing Pseudomonas aeruginosa

INTRODUCTION

The Carba NP test is a biochemical chromogenic assay developed to detect carbapenemase activity. Variable performance has been reported according to the type of carbapenemase and bacterial species involved. We aimed to describe the benefit of the Carba NP test and its commercial version, the RAPIDEC® CARBA NP, to detect carbapenemase-producing Pseudomonas aeruginosa.

METHODS

PubMed and ScienceDirect databases were searched. The following data was collected from each included study: research protocol, molecular profile of the tested strains, and sensitivity and specificity of the test used to detect carbapenemase-producing P. aeruginosa.

RESULTS

Thirty-four studies were included. The most frequently tested strains were metallo-beta-lactamase producers. The pooled sensitivity to detect carbapenemase-producing P. aeruginosa with the original Carba NP test, the Clinical and Laboratory Standards Institute (CLSI) Carba NP test, and the RAPIDEC® CARBA NP was 92%, 95%, and 96%, respectively. The pooled specificity was 99% with the original and the CLSI Carba NP tests, and 92% with the RAPIDEC® CARBA NP. Several studies evaluated modified versions of the Carba NP test to detect carbapenemase-producing P. aeruginosa, with reported sensitivity and specificity exceeding 90% in most cases.

CONCLUSION

The Carba NP test allows for fast screening and easy handling as well as optimal performance to detect carbapenemase-producing P. aeruginosa. These findings should be confirmed by further studies including a larger cohort of isolates and various types of carbapenemases, mainly non-metallo-beta-lactamases.

CPO Complete, a novel test for fast, accurate phenotypic detection and classification of carbapenemases

Carbapenemase-producing organisms (CPOs) are Gram-negative bacteria that are typically resistant to most or all antibiotics and are responsible for a global pandemic of high mortality. Rapid, accurate detection of CPOs and the classification of their carbapenemases are valuable tools for reducing the mortality of the CPO-associated infections, preventing the spread of CPOs, and optimizing use of new β-lactamase inhibitor combinations such as ceftazidime/avibactam, meropenem/vaborbactam and imipenem/relebactam. The current study evaluated the performance of CPO Complete, a novel, manual, phenotypic carbapenemase detection and classification test. The test was evaluated for sensitivity and specificity against 262 CPO isolates of Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii and 67 non-CPO isolates. It was also evaluated for carbapenemase classification accuracy against 205 CPOs that produced a single carbapenemase class. The test exhibited 100% sensitivity 98.5% specificity for carbapenemase detection within 90 minutes and detected 74.1% of carbapenemases within 10 minutes. In the classification evaluation, 99.0% of carbapenemases were correctly classified for isolates that produced a single carbapenemase. The test is technically simple and has potential for adaptation to automated instruments. With lyophilized kit storage at temperatures up to 38°C, the CPO Complete test has the potential to provide rapid, accurate carbapenemase detection and classification in both limited resource and technologically advanced laboratories.

The Global Ascendency of OXA-48-Type Carbapenemases

Surveillance studies have shown that OXA-48-like carbapenemases are the most common carbapenemases in Enterobacterales in certain regions of the world and are being introduced on a regular basis into regions of nonendemicity, where they are responsible for nosocomial outbreaks. OXA-48, OXA-181, OXA-232, OXA-204, OXA-162, and OXA-244, in that order, are the most common enzymes identified among the OXA-48-like carbapenemase group. OXA-48 is associated with different Tn1999 variants on IncL plasmids and is endemic in North Africa and the Middle East. OXA-162 and OXA-244 are derivatives of OXA-48 and are present in Europe. OXA-181 and OXA-232 are associated with ISEcp1, Tn2013 on ColE2, and IncX3 types of plasmids and are endemic in the Indian subcontinent (e.g., India, Bangladesh, Pakistan, and Sri Lanka) and certain sub-Saharan African countries. Overall, clonal dissemination plays a minor role in the spread of OXA-48-like carbapenemases, but certain high-risk clones (e.g., Klebsiella pneumoniae sequence type 147 [ST147], ST307, ST15, and ST14 and Escherichia coli ST38 and ST410) have been associated with the global dispersion of OXA-48, OXA-181, OXA-232, and OXA-204. Chromosomal integration of bla _OXA-48 within Tn6237 occurred among E. coli ST38 isolates, especially in the United Kingdom. The detection of Enterobacterales with OXA-48-like enzymes using phenotypic methods has improved recently but remains challenging for clinical laboratories in regions of nonendemicity. Identification of the specific type of OXA-48-like enzyme requires sequencing of the corresponding genes. Bacteria (especially K. pneumoniae and E. coli) with bla _OXA-48, bla _OXA-181, and bla _OXA-232 are emerging in different parts of the world and are most likely underreported due to problems with the laboratory detection of these enzymes. The medical community should be aware of the looming threat that is posed by bacteria with OXA-48-like carbapenemases.

Multidrug-resistant Gram-negative bacterial infections in solid organ transplant recipients-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of infections due to multidrug-resistant (MDR) Gram-negative bacilli in the pre- and post-transplant period. MDR Gram-negative bacilli, including carbapenem-resistant Enterobacteriaceae, MDR Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii, remain a threat to successful organ transplantation. Clinicians now have access to at least five novel agents with activity against some of these organisms, with others in the advanced stages of clinical development. No agent, however, provides universal and predictable activity against any of these pathogens, and very little is available to treat infections with MDR nonfermenting Gram-negative bacilli including A baumannii. Despite advances, empiric antibiotics should be tailored to local microbiology and targeted regimens should be tailored to susceptibilities. Source control remains an important part of the therapeutic armamentarium. Morbidity and mortality associated with infections due to MDR Gram-negative organisms remain unacceptably high. Heightened infection control and antimicrobial stewardship initiatives are needed to prevent these infections, curtail their transmission, and limit the evolution of MDR Gram-negative pathogens, especially in the setting of organ transplantation.

NDM Metallo-β-Lactamases and Their Bacterial Producers in Health Care Settings

New Delhi metallo-β-lactamase (NDM) is a metallo-β-lactamase able to hydrolyze almost all β-lactams. Twenty-four NDM variants have been identified in >60 species of 11 bacterial families, and several variants have enhanced carbapenemase activity. Klebsiella pneumoniae and Escherichia coli are the predominant carriers of bla _NDM, with certain sequence types (STs) (for K. pneumoniae, ST11, ST14, ST15, or ST147; for E. coli, ST167, ST410, or ST617) being the most prevalent. NDM-positive strains have been identified worldwide, with the highest prevalence in the Indian subcontinent, the Middle East, and the Balkans. Most bla _NDM-carrying plasmids belong to limited replicon types (IncX3, IncFII, or IncC). Commonly used phenotypic tests cannot specifically identify NDM. Lateral flow immunoassays specifically detect NDM, and molecular approaches remain the reference methods for detecting bla _NDM Polymyxins combined with other agents remain the mainstream options of antimicrobial treatment. Compounds able to inhibit NDM have been found, but none have been approved for clinical use. Outbreaks caused by NDM-positive strains have been reported worldwide, attributable to sources such as contaminated devices. Evidence-based guidelines on prevention and control of carbapenem-resistant Gram-negative bacteria are available, although none are specific for NDM-positive strains. NDM will remain a severe challenge in health care settings, and more studies on appropriate countermeasures are required.

Rapid detection of beta-lactamase production including carbapenemase by thin layer chromatography

OBJECTIVES

To develop a rapid and simple method that can identify the presence of β-lactamases in clinical isolates and samples, and determine their activity on different types of β-lactam antibiotics, including carbapenems, within one hour.

METHODS

In this study, we describe a thin layer chromatography-based method for rapid detection of β-lactamases including carbapenemases. The method relies on the examination of changes in the migration rate of β-lactams in chromatography, due to degradation by β-lactamase enzymes. A total of 44 isolates, 29 carbapenemase-producers and 15 non-carbapenemase-producers, were screened by this method.

RESULTS

The method has proven to be able to distinguish β-lactamases as carbapenemase or non-carbapenemase producing strains with high sensitivity in one hour.

CONCLUSIONS

The method developed, provides information about the production of β-lactamases by bacteria and β-lactam drugs inactivated by these enzymes, including carbapenems. This new method may play an important role in guiding antimicrobial treatment, especially in critically ill patients infected bacteria producing β-lactamases.

A novel GoldNano Carb test for rapid phenotypic detection of carbapenemases, particularly OXA type, in Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter spp

Objectives

To develop a simple gold nanoparticle (AuNP)-based colorimetric test, GoldNano Carb (GoldC), for detecting carbapenemase production in Gram-negative bacteria, compared with updated Carba NP (CNP) and CarbAcineto NP (CAcNP) tests by using PCR methods as gold standard.

Methods

Ninety-nine carbapenemase-producing Enterobacteriaceae (CPE), Pseudomonas spp. and Acinetobacter spp. isolates and 89 non-CPE isolates were tested by the GoldC and CNP. Additionally, the CAcNP was performed in the Acinetobacter spp. isolates. The final imipenem (imipenem/cilastatin form) concentration was 5 mg/mL for all three tests. For the GoldC, the imipenem powder was added directly to bacterial cell suspension in distilled water prior to detection of acid product by the citrate-capped AuNP solution. An AuNP change from red to purple, blue or green indicates carbapenemase activity.

Results

The GoldC detected all carbapenemase producers except one OXA-23-like producer (99.0% sensitivity), whereas 11 carbapenemase producers (10 Acinetobacter and 1 P. aeruginosa) were CNP negative (88.9% sensitivity). However, the GoldC and CNP provided 100% and 98.6% sensitivity, respectively, for the CPE and Pseudomonas spp. Both tests gave one false positive from CTX-M-1-like-producing Enterobacter spp. (98.9% specificity). The GoldC and CAcNP detected 96.7% and 93.3% of the Acinetobacter spp. isolates, respectively. Interestingly, times to positivity by the GoldC were markedly shorter than those by the CNP (76.8% versus 36.2% positive at 5 min) and CAcNP (43.3% at 5 min versus 20% within 30 min).

Conclusions

The GoldC is fast, easy, highly sensitive and inexpensive (∼$0.25 per test), suggesting that it may be suitable for routine carbapenemase detection in low-resource settings for infection control or epidemiological purposes.

Rapid Detection of Carbapenemase Production in Enterobacteriaceae by Use of a Modified Paper Strip Carba NP Method

Rapid and accurate detection of carbapenemase-producing Enterobacteriaceae (CPE) is important for preventing their spread in health care settings. We compared the performance of the Carba NP (CNP) test using the CLSI tube method with that using a modified paper strip method for the detection of carbapenemases in 390 Enterobacteriaceae isolates. The isolates were identified by Hong Kong's carbapenem-resistant Enterobacteriaceae surveillance program in 2016 and comprised 213 CPE and 177 carbapenemase-negative Enterobacteriaceae isolates. Molecular genotype was used as the reference. The test results were read at different time points for the CLSI method (1 min, 5 min, 1 h, and 2 h) and strip method (1 min and 5 min). The strip CNP and CLSI CNP tests correctly detect carbapenemase production in 93% and 93% of KPC producers, 100% and 38% of IMI producers, 94% and 85% of IMP producers, 98% and 90% of NDM producers, and 29% and 12% of OXA producers, respectively. Overall, the strip method has superior sensitivity to the CLSI method (86% versus 75%, respectively; P < 0.001, McNemar test). The specificity of both methods was 100%. By the CLSI method, 27%, 14%, 29%, and 6% of the CPE isolates were positive at 1 min, 5 min, 1 h, and 2 h, respectively. In contrast, by the strip method, 76% of the CPE isolates were positive at 1 min, and an additional 10% were positive at 5 min. In conclusion, the Carba NP test by use of the modified strip method has a higher sensitivity and a shorter assay time than that those by use of the CLSI tube method.

Evaluation of the rapid biochemical β-CARBA™ test for detection of carbapenemase-producing Gram-negative bacteria

We evaluated a rapid biochemical screening test β-CARBA™ for detection of Gram-negative carbapenemase producers. The sensitivity of the test after 30min incubation was 98.2%, but increased to 100% after 1h. β-CARBA™ proved reliable for carbapenemase screening in Acinetobacter spp. for which currently no commercial phenotypic assays are available.

Comparison of MALDI-ToF MS with the Rapidec Carba NP test for the detection of carbapenemase-producing Enterobacteriaceae

Although carbapenemase-producing Enterobacteriaceae (CPE) have become a serious public health issue, their detection remains challenging. The aim of this study was to implement a test based on imipenem hydrolysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS), using 65 strains producing or not a carbapenemase. Then, we compared its performance to that of the Rapidec Carba NP test using 20 additional strains. The MS-based test effectively discriminated between CPE and other non-carbapenem-susceptible strains compared to the Rapidec Carba NP test (sensitivity 100% and 92%, specificity 94% and 92%, respectively). The MS-based test gave less difficulty in interpretation than the colorimetric Rapidec Carba NP test. MALDI-ToF gave a result in less than one hour and limited the use of expensive molecular assays. In conclusion, the hydrolysis test based on MALDI-ToF MS can detect clinically relevant CPE isolates in routine practice. This technology, also described to screen for carbapenem resistance in Pseudomonas aeruginosa and Acinetobacter baumannii complex strains, also seems to be interesting in routine practice for these pathogens.

Evaluation of the Carba NP test for carbapenemase detection in Enterobacteriaceae, Pseudomonas spp. and Acinetobacter spp., and its practical use in the routine work of a national reference laboratory for susceptibility testing

The aim of this study was to evaluate the Carba NP test (and CarbAcineto) for the detection of carbapenemases in Enterobacteriaceae, Pseudomonas spp. and Acinetobacter spp., and to assess its usefulness in the routine work of the National Reference Centre for Susceptibility Testing (NRCST) in Poland. The evaluation of the Carba NP/CarbAcineto tests was carried out on a group of 81 Enterobacteriaceae, Pseudomonas spp. and Acinetobacter spp. isolates producing KPC-, NDM-, VIM-, IMP- or OXA-48, -23, -24/40, -58-type carbapenemases, and on 26 carbapenemase-negative strains cultivated on a broad panel of microbiological media. Subsequently, the performance of the Carba NP/CarbAcineto tests was assessed on 1282 isolates of Enterobacteriaceae, Pseudomonas spp. and Acinetobacter spp. from Polish hospitals, submitted to the NRCST during a 9-month period in 2014. The Carba NP/CarbAcineto results were compared with other phenotypic tests and/or polymerase chain reaction (PCR). The impact of the media on the results of the Carba NP/CarbAcineto tests was observed, with the Columbia blood agar yielding the highest sensitivity and clarity of the results. Furthermore, the Carba NP/CarbAcineto tests were included in the NRCST routine procedure for carbapenemase identification. The sensitivity and specificity of the Carba NP test were 95.8% and 93.3%, respectively, for Enterobacteriaceae, and 97.5% and 99.0%, respectively, for Pseudomonas spp. The sensitivity of the CarbAcineto test for Acinetobacter spp. was 88.9%. This study confirmed the usefulness of the Carba NP/CarbAcineto tests for the rapid detection of various types of carbapenemases.

Multicenter Performance Assessment of Carba NP Test

Eighty Gram-negative bacilli (54 Enterobacteriaceae and 26 nonfermenting Gram-negative bacilli) obtained from multiple institutions in the United States were distributed in a blinded manner to seven testing laboratories to compare their performance of a test for detection of carbapenemase production, the Carba NP test. The Carba NP test was performed by all laboratories, following the Clinical and Laboratory Standards Institute (CLSI) procedure. Site-versus-site comparisons demonstrated a high level of consistency for the Carba NP assay, with just 3/21 site comparisons yielding a difference in sensitivity (P < 0.05). Previously described limitations with bla_OXA-48-like carbapenemases and bla_OXA carbapenemases associated with Acinetobacter baumannii were noted. Based on these data, we demonstrate that the Carba NP test, when implemented with the standardized CLSI methodology, provides reproducible results across multiple sites for detection of carbapenemases.

Comparison of two rapid biochemical tests and four chromogenic selective media for detection of carbapenemase-producing Gram-negative bacteria

We evaluated RAPIDEC® CARBA NP, Neo-Rapid CARB, chromID® CARBA SMART (CARB/OXA), Brilliance™ CRE/ESBL, ChromArt CRE and BBL™ CHROMagar™ CPE for the detection of carbapenemase-producing bacteria. The analytical sensitivity of RAPIDEC® CARBA NP was better than that of Neo-Rapid CARB. A combination of carbapenemase and ESBL screening plates could be advantageous.

Comparative Evaluation of Four Phenotypic Tests for Detection of Carbapenemase-Producing Gram-Negative Bacteria

Four screening assays aimed for rapid detection of carbapenemase production from Gram-negative bacterial isolates, i.e., the Neo-Rapid Carb kit (Rosco Diagnostica A/S), the Rapidec Carba NP test (bioMérieux SA), the β Carba test (Bio-Rad Laboratories N.V.), and a homemade electrochemical assay (BYG Carba test) were evaluated against a panel comprising 328 clinical isolates (Enterobacteriaceae [n = 198] and nonfermentative Gram-negative bacilli [n = 130]) with previously characterized resistance mechanisms to carbapenems. Among Enterobacteriaceae isolates, the BYG Carba test and the β Carba test showed excellent sensitivities (respectively, 100% and 97.3%) and specificities (respectively, 98.9% and 97.7%). The two other assays yielded poorer performances with sensitivity and specificity of 91.9% and 83.9% for the Rapidec Carba NP test and of 89.2% and 89.7% for the Neo-Rapid Carb kit, respectively. Among Pseudomonas spp., sensitivities and specificities ranged, respectively, from 87.3% to 92.7% and from 88.2% to 94.1%. Finally, all tests performed poorly against Acinetobacter spp., with sensitivities and specificities, respectively, ranging from 27.3% to 75.8% and from 75 to 100%. Among commercially available assays, the β Carba test appeared to be the most convenient for routine use and showed the best overall performances, especially against OXA-48-like producers. The excellent performance of the BYG Carba test against Enterobacteriaceae was confirmed (100% sensitivity and 98.9% specificity).

Modification and evaluation of the Carba NP test by use of paper strip for simple and rapid detection of carbapenemase-producing Enterobacteriaceae

Carbapenemase-producing Enterobacteriaceae (CPE) isolates have now emerged worldwide. We therefore modified the phenotypic Carba NP test by use of a filter paper strip for easily and rapidly identifying CPE in routine laboratory. A collection of 56 CPE and carbapenemase-producing Pseudomonas spp. isolates (including 28 NDM-1, 11 IMP-14a, 1 IMP-1, 1 IMP-4, 1 IMP-9, 1 IMP-15, 4 VIM-2, 1 VIM-1, 1 IMP-14a with VIM-2, 3 OXA-48, 3 OXA-181 and 1 KPC-2 producers) and 41 non-CPE isolates (including 19 ESBL, 7 pAmpC, 3 AmpC, 9 ESBL with pAmpC and 3 non-ESBL & non-AmpC producers) as confirmed by the PCR methods were tested by the paper strip method using pharmaceutical imipenem/cilastatin as a substrate. Bacterial colonies of each isolate were applied directly on filter paper strips dropped with either imipenem-phenol red (test strip) or phenol red solution alone (control strip). The reaction was read within 5 min. This test failed to detect 3 OXA-181, 2 OXA-48 and 3 IMP-14a producers (85.7 % sensitivity), whereas no false positives were seen (100 % specificity). Further evaluation of the paper strip test in 267 CPE screening-positive isolates from three hospitals by their medical technologists showed 92.0 % sensitivity (100 % for NDM producers) and 100 % specificity compared with the PCR methods. Because of its ease, rapidness and cost effective, the paper strip test has a potential for routine CPE testing in low-resource laboratories particularly in areas with high prevalence of NDM enzymes, leading to appropriate antimicrobial therapy and infection control strategy.

Recent advances in the laboratory detection of carbapenemase-producing Enterobacteriaceae

Carbapenemase-producing Enterobacteriaceae (CPE), mainly Klebsiella pneumoniae and Escherichia coli, have been increasing rapidly on a global scale and are considered to be significant health threats. The most common carbapenemases are KPCs, NDMs, OXA-48-like, IMPs and VIMs but their distribution and prevalence differs between countries. The accurate, simple, cost effective and rapid detection of carbapenemases in clinical laboratories is an important initial step to control the spread of CPE within institutions. The diversity of carbapenemases in general, has challenged a simple approach for the detection of most types of CPE. This article summarizes the current and describes newer techniques available for the detection of carbapenemases among Enterobacteriaceae. The authors also provide a simplified approach for the accurate and rapid detection of CPEs that can easily be implemented in a clinical diagnostic laboratory.

Detection of carbapenemase-producing gram-negative bacteria using a simplified Carba NP test

A simplified Carba NP test (CNPt), the CNPt-direct, was evaluated for carbapenemase detection using 272 gram-negative bacteria. Compared to the Modified Hodge test, the CNPt-direct had higher sensitivity (98.2% vs. 71.6%). The simplified Carba NP is an accurate, cheap and simple test for rapid carbapenemase detection.